1. Field of Invention
This invention relates to an electric power distribution unit constituting an electric power distribution circuit extending from a vehicle-mounted electric power source in a vehicle, such as an automobile or the like, and an electric connection box having such a unit.
2. Description of Related Art
Heretofore, an electric connection box, in which an electric power distribution circuit is formed by stacking a plurality of bus bar boards, and in which fuses and relay switches are incorporated for distributing electric power from a common vehicle-mounted electric power source to various electronic units, has been generally known.
Further, in order to reduce a size of such an electric connection box and to implement switching control, an electric connection box has been developed recently in which semiconductor switching devices, such as field effect transistors (FETs) or the like, are interposed between input and output terminals in lieu of the relay switches.
However, since these semiconductor switching devices have a relatively great calorific power, it is necessary to efficiently remove heat from the devices.
An electric connection box is disclosed in, for example, Japanese Laid-Open Patent Application No. 2001-319708 as one way for solving this problem. The electric connection box includes an electric power distribution section having an input terminal to be connected to an electric power source, output terminals, semiconductor switching devices interposed between the input and output terminals, and a bus bar circuit section, having a metallic bus bar for forming a circuit and an insulation plate stacked on the bus bar, for connecting the respective output terminals of the electric power distribution section to vehicle-mounted loads. The electric power distribution section and bus bar circuit section are assembled in a common case with some of the bus bars in the bus bar circuit section being connected to the respective output terminals of the electric power distribution section.
In more detail, in the above-described electric connection box, the input terminal bus bar and a plurality of output terminal bus bars are disposed at a rear side of the heat radiation member, semiconductor switching devices are interposed between the input and output terminal bus bars for switching ON-OFF energization between the input and output terminal bus bars, and heat generated from the semiconductor switching devices is radiated through the heat radiation member to the outside. The output terminals of the electric power distribution section extend in a direction parallel to an insulating plate in the bus bar circuit section and are joined to the bus bars by welding or the like with the output terminals being stacked on the bus bars extending from the bus bar circuit section (stacked substantially parallel to an outer wall of the case in the insulating case).
According to such an electric connection box, since the electric power distribution section including the semiconductor switching devices and the heat radiation member is provided independently of the bus bar board as an electric power distribution unit, it is possible to efficiently cool the respective semiconductor switching devices at a single, concentrated position.
In order to weld output terminals of an electric power distribution unit and bus bars in a bus bar circuit in the above disclosure, a large working space is required between the terminals and the bus bars, and it is necessary to clamp them between welding electrodes at both sides so that they are stacked. Therefore, it is difficult to incorporate the electric power distribution unit in an electric connection box body and to connect the unit to the bus bar circuit afterward. Also, since the output terminals extend from the electric power distribution unit toward the bus bar circuit in a direction parallel to the bus bar board (a direction along an outer wall of a case), at least the projecting portions must be spaced between the electric power distribution unit and the bus bar circuit. This increases the space occupied by the electric connection box.
In view of the above problems, an object of the present invention is to provide an electric power distribution unit that can be easily incorporated in an electric connection box without upsizing the whole electric connection box and to provide an electric connection box that can efficiently cool switching devices while downsizing the electric connection box and simplifying a structure of a bus bar board in connection with providing the electric power distribution unit.
In order to solve the above problems, the present invention is directed to an electric power distribution unit including: a heat radiation member; a plurality of unit-forming bus bars connected to a first surface of the heat radiation member; and switching devices mounted on the unit-forming bus bars. Ends of the unit-forming bus bars extend outwardly from the periphery of the heat radiation member. The extending ends are bent toward the heat radiation member. The bent ends face the bus bars of the bus bar board and are connected to the bus bars to form input terminals and output terminals. Electric power inputted to the input terminals is supplied through the switching devices to the output terminals to form a circuit. The switching devices may be semiconductor switching devices.
A bus bar board including a plurality of bus bars constituting an electric power circuit is accommodated in an insulating case. Ends of given bus bars in the bus bar board stand up on a front side of the insulating case to form connection terminals. An electric power distribution unit is accommodated in the insulating case with the heat radiation member being directed to a front side of the insulating case and the switching devices being directed to a rear side of the insulating case, and the input and output terminals confronting and being connected to the connection terminals.
According to the above construction, since the electric power distribution unit including the switching devices is formed independently of the bus bar board, it is possible to concentratedly cool the switching devices by a common heat radiation member. Accordingly, it is possible to efficiently cool all the respective switching devices while maintaining a small occupied space of the heat radiation member in comparison with a conventional electric power distribution unit in which the switching devices are mounted on the bus bar board in a spread-out manner.
When it is necessary to change the switching devices due to a change of the electrical current to be used, this change can be accomplished simply by exchanging the electric power distribution unit, without changing the bus bar board. This is superior in general versatility. It is also possible to exchange the electric power distribution unit for a relay block in an existing electric connection box using a relay.
Furthermore, since the ends of the input and output terminal bus bars of the electric power distribution unit are bent toward the heat radiation member to form input and output terminals, it is possible to accommodate the input and output terminals and heat radiation member in the electric connection box so that they are directed to the outside. Because of this, it is possible connect the input and output terminals and the bus bars at the electric connection box body to one another, by welding, for example, while ensuring a good heat radiation function of the heat radiation member and to reduce the occupied space of the whole electric connection box while maintaining a small distance between the electric power distribution unit and the bus bar board. In addition, since the switching devices mounted on the input and output terminal bus bars are directed to a rear surface of the electric connection box, it is possible to effectively protect the switching devices.
It is preferable to incorporate a control circuit board that controls driving of the switching devices in the electric power distribution unit. This makes it possible to accommodate the whole electric power distribution unit in a body of the electric connection box with the control circuit board being electrically connected to the switching devices beforehand. The work of assembling the electric connection box can therefore be dramatically simplified in comparison with a work of assembling the electric power distribution unit and control circuit board individually.
In this case, if the control circuit board is disposed facing the rear surface of the heat radiation member, the control circuit board is necessarily directed to the rear side of the insulating case when the electric power distribution unit is mounted in the insulating case of the electric connection box. This can effectively protect not only the switching devices but also the control circuit board against any objects outside the case.
As a practical structure for electrically interconnecting the control circuit board and the semiconductor switching devices, portions of the unit-forming bas bars to which the switching devices are connected may be bent up to form board connection terminals standing up from the rear surface of the heat radiation member and the control circuit board may be connected to the board connection terminals. According to this structure, it is possible to electrically interconnect the switching devices and the control circuit board by merely bending a part of the unit-forming bus bars.
It is possible to select a suitable configuration and structure of the insulating case. For example, (1) a connector-forming section on which a plurality of connector housings which, along with bus bar ends extending from the bus bar board, constitute connectors that can be connected to external connectors, (2) a unit-mounting section on which the electric power distribution unit is mounted, and (3) a plurality of electrical component-fitting sections that have configurations in which electrical components (e.g., fuse elements) can be fitted and electrically interconnect the electrical components and ends of the bus bars extending from the bus bar board may be arranged parallel to the bus bar board in the insulating case. This will facilitate connections and exchange between an external connector and the bus bar board, between the bus bar board and the electric power distribution unit, and between the bus bar board and the electrical components on the same surface of the insulating case. Since the connector-forming section, unit-mounting section, and electrical component-mounting section are arranged in a direction parallel to the bus bar board, it is possible to connect the respective external connectors, the electric power distribution unit, and the respective electrical components to the common bus bar board at a small distance, thereby enabling the whole electric connection box to be assembled in a compact manner.
Preferably, the electric power distribution unit includes bus bars directly fitted in electrical component terminals for the electrical components to be mounted on the insulating case of the electric connection box. According to this construction, it is possible to directly interconnect suitable unit-forming bus bars of the electric power distribution unit and the electrical components without disposing the bus bar board between them, thereby simplifying a wiring structure.